MicroRNAs (miRNAs) are an abundant class of short endogenous RNAs that act as post-transcriptional regulators of gene expression by base-pairing with their target mRNAs. They are processed from longer (ca 70-80 nt) hairpin-like precursors termed pre-miRNAs by the RNAse III enzyme Dicer. MicroRNAs assemble in ribonucleoprotein complexes termed miRNPs and recognize their target sites by antisense complementarity thereby mediating down-regulation of their target genes. Near-perfect or perfect complementarity between the miRNA and its target site results in target mRNA cleavage, whereas limited complementarity between the microRNA and the target site results in translational inhibition of the target gene.
A summary of the role of microRNAs in human diseases, and the inhibition of microRNAs using single stranded oligonucleotides is provided by WO2007/112754 and WO2007/112753, which are both hereby incorporated by reference in its entirety. WO2008046911, hereby incorporated by reference, provides microRNA sequences which are associated with cancer. Numerous microRNAs have been associated with disease phenotypes and it is therefore desirable to provide substances capable of modulating the availability of microRNAs in vivo. WO2007/112754 and WO2007/112753 disclose short single stranded oligonucleotides which are considered to form a strong duplex with their target miRNA. SEQ ID NOs 1-45 are examples of anti microRNA oligonucleotides as disclosed in WO2007/112754 and WO2007/112753.